Various types of well stimulation fluids are used in hydraulically fracturing of oil and/or gas wells to enlarge or create new well formation fractures making it possible for oil and/or gas to move more readily to a well bore. A fracturing or frac fluid is hydraulically injected into the well and generally includes various gelling agents to thicken the fluid and reduce friction and includes selected particles or propping agents to hold the fracture open after the applied pressure is relieved, and may contain a wide variety of chemical additives to overcome different types of well formation conditions which may be encountered. The base fluid may contain various combinations of fresh or salt water, various hydrocarbons or well fluids. Many types of gelling agents are used such as synthetic polymers and guar gum. The propping agents may be sand, prepared particles, or ground up walnut shells. The chemical additives may include acids, breakers, friction reducers, surfactants, and other dry and wet chemical aids.
It has been conventional to combine the gelling agents and the base fluid in tanks prior to commencing the fracing operation. Upon commencing the operation, the combined gel and base fluid was pumped into a mixing vat for combining with the propping articles and the mixed slurry was then pumped to the frac pumps for injection into the well. However, this process required that the combined base fluid and gel be premixed, which is a considerable expense. Furthermore, the gelled fluid is expensive and if the operation is stopped or the gelled fluid is not all used, another expense is incurred along with the expense and trouble of disposing of the unused gelled fluid. Furthermore, the stored gelled fluid is subject to degradation.
The present invention is generally directed to an apparatus for blending all of the well stimulation fluids used for hydraulic fracturing while proportioning and mixing the required components of the stimulation fluid as the hydraulic fracturing operation proceeds.